Embodiments of the disclosure relate generally to a buck-boost converter and a method for regulating an output voltage, and more particularly to a buck-boost converter and a method for regulation through bucking or boosting an input voltage.
Busk-boost converters may be used to produce a constant DC output voltage, notwithstanding a DC input voltage which may be higher, lower, or equal to the output voltage. They may operate in a buck mode, a boost mode, and/or a buck-boost mode. The converter is considered to be in a buck mode of operation when the input voltage is higher than the output voltage, in a boost mode of operation when the input voltage is lower than the input voltage, and in a buck-boost mode of operation when the input voltage is approximately the same as the output voltage. The buck-boost mode of operation is a transition between the buck mode and the boost mode.
The buck-boost converter includes a number of switches. The output voltage is regulated through regulating open time of the switches. The buck-boost converter generates modulating signals based on duty cycles to regulate the switches. The buck-boost converter includes an error controller configured to generate the duty cycles. In the buck mode of operation, the output voltage Vout=D*Vin, wherein D is the duty cycle, Vin is the input voltage. In the boost mode of operation, the output voltage Vout=1/(1−D)*Vin. When the output voltage is equal to the input voltage, the duty cycle D is equal to 100% that is calculated from the expression of the output voltage in the buck mode, while the duty cycle D is equal to 0% that is calculated from the expression of the output voltage in the boost mode. Accordingly, the duty cycle generated by the error controller is jumped from 100% to 0% or from 0% to 100% during the transition between the buck mode and the boost mode, so that it is difficult to control the output voltage smoothly by one error controller during the transition.
It is desirable to provide a solution to address at least one of the above-mentioned problems.